Influence of fused deposition modeling process parameters on the transformation of 4D printed morphing structures

Abstract

4D printing combines additive layer manufacturing processes with smart materials to create structures that are able to change shape or properties over time under the influence of environmental stimuli. The article presents 3D printed multi-material shape-variable structures imitating a hinge. Fused deposition modelling was used because it provides the ability to pre-program structures during the printing process by varying printing parameters. The structures are printed with PLA and TPU and remain flat after printing until they are exposed to a stimulus - heat. The main objective of this article is to present the possibilities of the aforementioned pre-programming step which can be adapted by varying the printing process and design parameters of the printed part. Experimental results are presented investigating the influence of printing speed, temperature of the build plate and number of active layers in the structure. Furthermore, the repeatability of deformations after a small number of cycles is investigated. The obtained results prove that the deformation of the structures can be controlled by printing parameters and a variety of bending degrees can be obtained by manipulating them. Hot water is used as a stimulus in the study to activate the structures but it is believed that other direct and indirect heating sources are also applicable. The research could help predict the behaviour of deformation of shape-morphing structures by selecting certain printing and design parameter values.

Effect of Printing Process Parameters on the Shape Transformation Capability of 3D Printed Structures

“…The printing speed influences the shape transformation. Higher printing speed produces higher residual stress and as a result, higher shrinkage ratio [ 9 , 15 , 28 , 29 , 30 ]. Higher printing speed also leads to a less accurate extrusion process and lower print quality [ 31 ].…”

“…In the second case, it is controlled by the multi-material structure, consisting of active and passive segments. For the active segment, a combination of polymers that differ in thermal transition temperatures and have different physical and mechanical properties is used [ 9 , 15 ]. One of the polymers, the active one, shrinks when heated above its Tg, and the second polymer, called the passive material, remains unchanged and serves only as a support for the active material to twist in a certain direction and plane.…”

“…However, only one, i.e., the passive material, is used for the passive, inactive segment of the 3D printed structure. One article reported that single layer mono-material structures produce highly varying, unpredictable bending-twisting motions which are not desirable [ 15 ].…”

Fused Filament Fabrication-4D-Printed Shape Memory Polymers: A Review

“…Kačergis et al [ 72 ] studied 3D-printed multi-material shape-variable structures imitating a hinge. Using the FFF process, different printing parameters were analysed.…”

Advances in additive manufacturing of shape memory polymer composites

“…The possibility of Thermoform opens a few future avenues for the SMPC world, such as remote activation of the 3 D printed shape. Following this work, Kacergis et al investigated the printing parameters for 4 D printing based on bilayer PLA/TPU composites but suggested that surrounding heat activation might not be the best choice to achieve field applications of 4 D printing (Kačergis et al, 2019). Garces and Ayranci (2018), Garces and Ayranci (2020) proposed the 3 D printing of SMPU with a Graphene oxide/PLA bilayer composite.…”